Effects loop issue with Mark V SQUEALING

[delt4]

I'm using a 4 cable method to hook up my effects board ( Pod HD500 ) to my Mesa Mark V head. I am not using any cab sims nor am I using amp models. This is strictly for effects only.

Problem is, every once in a while, ( did it last 2 practices ) when activating the Mesa loop on my Mark V pedal, I'll get this extremely load squealing sound and I will have to rehearse without the POD. THE FUNNY THING is, I'll come back next week, and without changing ANY settings on the Pod or the Mesa, the amp and the Pod will work fine. I cannot replicate this issue on demand.

Some things I've tried.

All new tubes
plugging the pod and the amp into different outlets
turning on either the amp or the pod first
tried the pod in 2 cable method ( just thru loop only, still got the squeal )
I'm at a total loss here, and would like some other diagnostic suggestions to try.

Other than the effects problem, amp works great.

 

[JEB3]

Is your HD500 software up to date? suggest researching the line6 forum, if you have not done that already.

 

[screamingdaisy]

I don't know if this is your problem or not, but a lot of people run the channel masters too hot and overdrive the effects/effects loop.

To fix it turn the channel master on channel 3 down to 9:00, then adjust the volume of the other two channels to balance the third.

If this is too quiet then turn the volume back up using the master output.

 

[delt4]

Thanks so far for the responses.. I'm aware of the channel volumes, so I try and keep an eye on that. I would like to know how everything could work one week, then come back next week and it starts that loud squealing when the effect button is engaged. I'll keep poking around on it.

 

[Mungo Zen]

Can you try the POD on another amp or another device in the loop of the Mark V? Based upon what you have stated I am thinking this is something related to the POD.

My thought process is, a loud squeal when engaging the loop could be a high gain/high volume boost coming in the line. Would it be possible that the times the issue has happened the POD was not on the expected channel, or had been restarted or the like?

 

[delt4]

Mungo, that's a great idea and I was thinking of the same thing. Last practice, we were in a bit of a hurry to get to practicing, so I just disconnected the POD and practiced, sans effects. I plan on trying my pod500 hooked up to my other guitar players amp, which is an express 5:50..... I will also try his effects unit in my amp as well.

Usually issues like this will happen all the time.... ie.... usually you have an issue or you don't. Mine seems to come every once in a while, even if no settings were changed on the POD and the amp.... This makes it much harder to troubleshoot and effectively replicate the issue, which would then lead me to a clearer path of isolating the issue.

Is there a way to measure the input level of the signal coming into my Mark V head from the POD? I suspect this is much higher when I get that very loud squeal, as opposed to a lower level when I do not get the squeal.

******** on a side note, we had an issue with our bass rack mount amp, which is a Mesa Boogie M3 Carbine. For some reason, when running the DI out to the mixing board, we couldn't understand why the amp produced a ground loop hum thru the pa ( amp worked just fine, but thru the PA system there was a hum ). Turned out, that you need to plug in the Mesa M3 into the same outlet as the mixing board in order for the DI to work through the PA. We did a large festival, and the sound guy hooked up some isolation box, which also solved the problem....

 

[jb's 52]

When it squeals again, maybe try the POD in front of the amp. If it squeals there, you can eliminate the effect loop.
IIRC there's a "pad" switch that messes with input sensitivity. Maybe that's getting bumped making the POD overly sensitive thus causing it to squeal.

 

[elvis]

I have a similar thing that happens when I have a ground loop.

Plug all equipment into the same outlet. Make sure you don't have a stray path. For me it was through a DI box to the PA. Once I lifted that GND it went away. I figured it out because I plugged into the PA at rehearsal but not at home, so with the same everything I was getting squeals sometimes and not others.

GND loops are not always a hum or buzz.

 

[delt4]

Elvis, that's interesting. I need to more closely monitor what is getting hooked up and where! I suspect, but may be wrong, that if the effects unit works normally most times and some times it doesn't, without me changing ANY settings, it could be a loop problem!

Oh well, will see this weekend.... :?

 

[OldTelecasterMan]

I had this happen. Unplugged everything trying to track it down...and then it was gone. I put everything back just as it was. So I'm kinda at a loss myself.

 

[delt4]

OldTelecasterMan, so that happened just once, or more than that?

 

[delt4]

I know that I started this thread a while back ago, but just wanted to give a quick update. As I've posted above, I've had random intermittent issues every once in a blue moon with squealing on my Mark V head when activating the effects loop that would come and go. This past weekend, I think I've found a way to replicate this issue. I noticed that when I was attempting to mic my cab ( recto 2x12 ) that I didn't have a mic stand. I had a Sennheiser microphone ;this one

I could just drape it down over the speaker by running the xlr cable underneath the head. When I lifted one end of the head up to run the cord and set the head head back down and actually dropped the head about 1/8th of inch the squeal started. I already had the loop engaged when this happened.
I got rid of the squeal by gently hitting the side of the head to see if some sort of tapping would do it, and wouldn't you know, the squealing went away.

I think that the V6 tube controls the effects loop. Could there be an issue with the tube or the tube socket in itself?

 

[jb's 52]

I think that the V6 tube controls the effects loop. Could there be an issue with the tube or the tube socket in itself?

Could be a pre-amp tube going microphonic. Put it in "hard bypass" and test like this:

https://www.youtube.com/watch?v=wSl-l9aWDHw&feature=youtu.be&t=9m28s

 

[ATR1]

V6 is your pre-amp tube for loop try swapping with new one. Also pick up a couple of HUMBUSTER cables from Bes-tronics to help with any outside interference.. TRS side at effects unit TS to AMP.

 

[OldTelecasterMan]

OldTelecasterMan, so that happened just once, or more than that?

Turned out to be a foul.. not shorted, not open.. foul cable. It sorta worked.. it poorly worked. Sometimes it worked fine... sometimes it acted strangely.

 

[delt4]

Everyone, thanks for the ideas so far... Got the amp back home, I will try to detect for any microphonic tubes.

OldTelecasterMan: Which cord was it, out of the 4, if I'm assuming correctly that you were/are running 4 cable method?

ATR1: Thanks for the ideas.


My head/effects unit acted up again at practice today. Was fine the night before at the other practice place. I thought that by lightly moving or tapping the side of the head would alleviate the issue, but today, had no effect. Was pissed....

 

[OldTelecasterMan]

Well, I have a pretty elaborate rig. It has four 2x12 cabinets. 2 vertical 2x12 and 2 compact 2x12. The vertical cabs run direct from the head with a cab clone sending line level to strymon bluesky reverb and an Ola chorus to a stereo power amp to the compact 2x12 cabs. Lots of room for cable failure. A rotovibe, crybaby and phase90 in front of the amp. With two mxr carbon copy delays in the loop. It's freakin crazy but awesome big sound. I split one vert. And one compact on each side of the stage.

 

[delt4]

Well, I've finally found the issue, and it was with the cord that goes from the amp return to the Pod500. It needs to be bent a certain way and then the amp will start squealing with the loop engaged. Just glad it wasn't a major issue with the Mark V head or the Pod itself. Don't need the hassle of sending stuff back in for repairs.

Thanks everyone, especially OldtelecasterMan and lesson learned..... Be diligent about checking ( thoroughly ) the most obvious things first.

 

[OldTelecasterMan]

Ah yes the (sad) cable was at the time I found it failing, connected to the head. Not that is always connected to the head. I used to just grab cables one with a red ring and one with a yellow and run them where I needed them. Send, return or Right and left for whatever I needed, red, yellow, red, yellow bla bla bla. There are a few spares so one of them goes into the head and the rest back into the bag. The cable that failed was a "Monster" cable... I quit buying them. This was my second Monster cable fail. The first one died with a problem about 12 inches from the end.

I have been using Mesa Boogie branded, 14 gage, Quantum Audio Design Q-2300 EPI series oxygen free cables. The Mesa Store in Hollywood sells them. It's a very heavy cable, so far very durable, it is also a very stiff cable. It is for amps and pedalboards but not designed to plug into guitars...

http://quantumaudiodesigns.com/QATCATV.2.pdf Scroll down to the EPI section.

 

[delt4]

I checked out the page, thanks for the link. They look like good cables.